Production of nitriles



Patented Oct. '5, 1948 UNITED STATES PATENT OFFICE PRODUCTION OFNITRILES William I. Denton, Woodbury, and Richard B.

Bishop, Haddoniield, N. J assignors to Socony- Vacuum Oil Company,Incorporated, a corpora tion of New York No Drawing. ApplicationFebruary 1, 1946, Serial No. 645,013

12, Claims. 1 This invention relates to a process for producing'nitriles having at least two carbon atoms, and

is more particularly concerned with a catalytic tively high cost of thereactants employed and/or the toxic nature of some of the reactantsand/or the number of operations involved in their. ultimate preparation.For example. aliphatic nitriles have been synthesized by oxidizinghydrocarbons to acids followed by reacting the acids thus obtained withammonia in the'presence of silica gel. Other methods involve reactingalkyl halides with alkali cyanides reacting ketones with hydrogencyanide in the presence of dehydration catalysts, etc, Aromatic nitrileshave been synthesized .by reacting alkalicyanides with aromatic.sulionates or with aromatic-substituted alkyl halides; by reacting morecomplex cyanides such as potassium cuprous cyanide with diazoniumhalides) by. reacting isothiocyanates with copper or with zinc dust: andby reacting aryl aldoximes with acyl halides.

We have now found a process for producing nitriles which is simple andinexpensive, and which employs non-toxic reactants.

We have discovered-that nitriles containing at least two carbon atomscan be prepared by reacting paraillnic hydrocarbons having at least twocarbon atoms, with'az'nmonia, at elevated temperatures, in the presenceof catalytic material containing molybdenum oxide or tungsten oxide. Ourinventionis tobe distinguished from the conventional processes for theproduction of hydrogen cyanide wherein carbon compounds, such as carbonmonoxide, methane,'and benzene, are

.reacted with ammonia at elevated temperatures in the presence ofalumina, nickel, quartz, clays, oxides of thorium and cerium, copper,iron oxide, silver, iron, cobalt, chromium, aluminum phosphate, etc. Theprocess of the present invention is also to be distinguished from theprocesses of the prior art for the production of amines whereinhydrocarbons are reacted with ammonia at high temperatures, or at lowertemperatures in the presence of nickel.

Accordingly, it is ,an object or the present invention to provide aprocess for the production of nitriles containing at least two carbonatoms. Another object is to afiord a catalytic process for a theproduction of nitriles containing at least two carbon atoms. Animportant object is to provide a process for producing nitrilescontaining at least two carbon atoms whichv is inexpensive andcommercially feasible. A specific object is to provide a process-forproducing nitriles containing at least two carbon atoms from paraflinichydrocarbons having at least two carbon atoms. Other objects andadvantages of the present invention will become apparent to thoseskilled in the art from the following description.

Broadly stated, our invention provides an inexpensive and commerciallyfeasible process for the production of nitriles containing at least twocarbon atoms, which comprises reacting a paraflinic hydrocarbon havingat least two carbon atoms, with ammonia, in the gaseous .phase and atelevated temperatures, in the presence of catalytic material containinga metal. oxide selected from the group consisting of molybdenum oxideand tungsten oxide. 1

Generally speaking, any paraflinic hydrocarbon having at least twocarbon atoms issuitable as the hydrocarbon reactant .in the process ofour invention. Ethane, propane, pentane, butane, isobutane, hexane,methyl hexane, dimethyl pentane, heptane, cetane, octadecane, etc., maybe mentioned by way of non-limiting examples. 'It

. tions serve the purposes of the present invention. It is to beunderstood also, that hydrocarbon mixtures containing one or moreparafllnic hydrocarbons having 'at least two carbon atoms,

may also be used herein, and that when such mixtures are used, thereaction conditions, such as contact time, will be slightly different inview of the dilution effect of the constituents present with theparamnic hydrocarbon or hydrocarbons having at least two carbon atoms.Accordin ly,

' paramnic hydrocarbons having at least two carbon atoms, mixturesthereof, and hydrocarbon mixtures containing one or more of suchparafllnic hydrocarbons may be used.

Although any parafiinic hydrocarbon having at least two carbon atoms maybe utilized in our process, we especially prefer to use those containingbetween two and about ten carbon atoms, and of these, propane, butaneand heptane are especially preferred. I

The proportions of reactants, i. e., paramnic hydrocarbon having atleast two carbon atoms and ammonia used in our process may be variedover a wide range with little effect on the conversion per pass andultimate yield. In general, the charge of reactants may contain aslittle as 2 mol. per cent or as much as 98 mol. per cent of paramnichydrocarbons. In practice, however, we use charges containing betweenabout 20 mol. per cent and about 90 mol. per cent of paramnichydrocarbon, and ordinarily, we prefer to use charges containing a molarexcess of ammonia over the parafhnic hydrocarbon reactant.

We have found that the catalysts to be used to produce nitrilescontaining at least two carbon atoms, by reacting paraflinichydrocarbons having at least two carbon atoms with ammonia, are thosecontaining a molybdenum oxide or a tungsten oxide, such as molybdenumsesquioxide (Mom), molybdenum dioxide (M002), molybdenum trioxide(M003), molybdenum pentoxide (M0295), tungsten dioxide (W02) andtungsten trloxide (W03). Therefore, and in the interest of brevity, itmust. be clearly understood that when we speak of molybdenum oxide or oftungsten oxide herein and in the claims, we have reference to thevarious oxides of molybdenum and tungsten. While all of these metaloxides are operative in the present process, they are not equivalent intheir eflectiveness from the standpoint of catalytic activity, tungstenoxide (W02) for example, being far less effective than molybdenumtrioxidev (M003) the latter being the preferred starting catalyticmaterial.

While. these oxides exhibit different degrees of effectiveness when usedper se, they generally possess additional catalytic activity when usedin conjunction with the well known catalyst supports, such as alumina,silica gel, carborundum, pumice, clays and the like. We especiallyprefer to use alumina (Anon as a catalyst support, and we have foundthat a catalyst comprising molybdenum trioxide supported. on alumina isparticularlyuseful for ourpurpose. Without any intent of? limiting thescope of the pres- 4 I eat invention, it is suspected that the enhancedcatalytic activity of thesupported catalysts is attributable primarilyto their relatively large surface area. I

The concentration of catalytic metal oxide in the supported.- catalystsinfluences the conversion per pass. In general, the conversion per passincreases with increase in the concentration of metal oxide. Forexample, we have found that a catalyst comprising 20parts by weight ofmolybdenum trioxide on parts by weight of alumina is more eifective thanone comprising 10 parts by weight of molybdenum trloxide on parts byweight of alumina. It is to be understood, however, that supportedcatalysts containing larger or smaller amounts of the catalytic metaloxides may be used in our process. I

We have found also that in order to obtain initial maximum catalyticefllciency, particularly where the catalytic material comprises thehigher catalytic metal oxides, that the catalysts should be conditionedprior to use in the process. As defined herein, conditioned catalystsare those which have been exposed to ammonia or hydrogen, or both, for aperiod of time, several minutes to several hours, depending upon thequantity, at temperatures varying between about 800 F. and about 1300 F.However, if desired, the conditioning treatment may be dispensed withinasmuch as the catalyst becomes conditioned during the initial stagesof our process when the catalyst comes in contact with the ammoniareactant.

In operation, the catalysts become fouled with carbonaceous materialwhich ultimately aifects their catalytic activity. Accordingly, when theefiiciency of the catalyst declines to a point where further operationbecomes uneconomical or disadvantageous from a practical standpoint, thecatalyst may be regenerated, as is well known in the art, by subjectingthe same to a careful oxidation treatment, for example, by passing astream of air or air diluted with flue gases over the catalyst underappropriate temperature conditions and for a suitable period of time,such as the same period of time as the catalytic operation. Preferably,the oxidation treatment is followed by a purging treatment, such aspassing over the catalyst a stream of purge gas, for example, nitrogen,carbon dioxide,hydrocarbon gases, etc.

The reaction or contact time, i. e., the period of time during which aunit volume of the reactants is in contact with a unit volume ofcatalyst, ma vary between a fraction of a second and several minutes.Thus, the contact time may be\as low as 0.01 second and as high as 20minutes. We prefer to use contact times varying between 0.1 second andone minute, particularly, between 0.3 second and 30 seconds.

In general, the temperatures to be used in our process vary betweenabout 850 F. and up to the decomposition temperature of ammonia (about1250-1300 F.), and preferably, temperatures varying between about 925-F. and about 1075 F. The preferred temperature to be used in anyparticular operation will depend upon the nature of hydrocarbon reactantused and upon the type of catalyst employed. Generally speaking, thehigher temperatures increase the conversion per pass but they alsoincrease the decomposition of the reactants thereby decreasing theultimate yields of aliphatic nitriles. ingly, the criteria fordetermining the optimum temperature to be used in any particular opera-Accord- 1 charge materials condense more readily.

tion will be-based on the'nature of the parafllnic hydrocarbon reactant,the type of catalyst, and a consideration of commercial feasibilityirgmthe standpoint of striking a practical balan'eet'be-v tween conversionper pass and losses to" decomposition.

QAIBQOSG rently, or countercurrently, with the reactants.

The vapors of the reactants are maintained in contact with the catalystat a predetermined elevated temperature and for a predetermined periodThe process of the present invention may be is evident from the law ofLe Chatelier-Braun that the equilibrium favors nitrile formation more atreduced pressures. However, such pressures reduce the throughput of thereactants and present increased difliculties in recycling unreactedcharge materials. Therefore, atmospheric pressure or superatmosphericpressures are preferred.

At the present time, the reaction mechanism involved in the process ofthe present invention is not fully understood. Fundamentally, thesimplest possible method of making nitriles is to introduce nitrogendirectly into a hydrocarbon molecule, thereby avoiding intermediatesteps with their accompanying increased cost. In our process, we havenoted that considerable amounts of hydrogen are evolved; that whenparafllnic hydro carbons higher thanethane are employed, that aliphaticnitriles having fewer carbon atoms than the parafiinic hydrocarbonreactant predominate in the reaction product; and that when paraflinichydrocarbons having at least six carbon atoms in a straight chain areemployed, that aromatic nitriles as well as aliphatic nitriles areformed. Hence, it is postulated, without any intent of limiting thescope of the present invention. that in our process, the aliphaticnitriles are formed in accordance with they following equations, usingbutane as an example:

1. H11 HI! or by formation of the corresponding oleilnic hydrocarbonfollowed by the replacement of hydrogen with nitrogen therein; and that.the aromatic nitriles are formed by cyclization of the paraflinichydrocarbons having at least six carbon atoms in a straight chain,followed by dehydrogenation and introduction of nitrogen therein.

The present process maybe carried out by making use of any of thewell-known techniques for operating catalytic reactions in the vaporphase effectively. By way of illustration, butane and ammonia may bebrought together in suitable proportions and the mixture vaporized in apreheating zone. The vaporized mixture is then introduced into areaction zone containing a catalyst of the type defined. hereinbefore.The reaction zone may be a chamber of any suitable type useful incontact-catalytic operations; for

of time, both as set forth hereinbefore, and the resulting reactionmixture is passed through a condensing zone into a receiving chamber. Itwill be understood that when the catalyst flows concurrently,orcountercurrently, with the reactants in a reaction chamber, thecatalyst will be thereafter suitably'separated from the reaction mixtureby filtration, etc. The reaction mixture will be predominantly a mixtureof aliphaticnitriles, hydrogen, unchanged butane, and unchanged ammonia.

The aliphatic nitriles and the unchanged butane will be condensed inpassing through the condensingzone and will be retained in the receivingchamber. The aliphatic nitriles can be'separated be separated from eachother. The unchanged butane and ammonia can be recycled, with or withoutfresh butane and ammonia, to. the process. I

It willbe apparent that the process may be operated as a batch ordiscontinous process as by using a catalyst-bed-type reaction chamber inwhich the catalytic and regeneration operations alternate. With a seriesof such reaction chambers, it will be seen that as the catalyticoperation is taking place in one or more of the reaction chambers,regeneration of the catalyst will be taking place in one or more of theother reaction chambers. correspondingly, the .process may be continuouswhen we use one or more catalyst chambers through which the catalystflows in contact with the reactants. In such a continuous process, thecatalyst will flow through the reaction zone in contact with thereactants and will thereafter be separated'from the reaction mixture as,for example, by accumulating the catalyst on a suitable filter medium,before condensing the reaction mixture. In a continuous process,therefore, the catalyst-fresh or regenerated-and the reactants-fresh orrecycle-'- will continuously flow through a reaction chamber.

'The following detailed examples are for the closed therein or to themanipulations and conexample, a catalyst bed contained in a shell, or

ditions set forth in the examples. As it will be apparent to thoseskilled in the art. "a wide variety of other paraiiinic hydrocarbons maybe use.

A reactor consisting of a shell containing a catalyst chamber heated bycirculating a'heattransfer medium thereover, and containing 100 partsbyweight of catalyst comprising 10 parts by weight of molybdenum trloxidesupported on parts by weight of activated alumina was used. The catalystwas prepared by soakingcommercial activated alumina in an aqueoussolution of 7 ammonium molybdate, followed by heating of the thustreated alumina to drive off ammonia and water. The catalyst wasconditioned by passing a stream of ammonia thereov'er for 45 minutes at900 F. Ammonia and a parafllnic hydrocarbon were introduced in the vaporphase into the reactor. The reaction mixture was 7 passed from thereactor, through a condenser, into a receiving chamber. The nitriieswere then separated from the unchanged ammonia and paramnic hydrocarbonreactant. For convenience, the pertinent data oi each run are set forth1075 F., in the presence of a catalyst comprising a molybdenum oxide.

5. A process for the production of nitriles having at least two carbonatoms per molecule, which comprises contacting propane with ammonia, in

4. A process for the production oi. nitriles having at least two carbonatoms per molecule, which comprises contacting propane with ammonia, ingaseous phase,at temperatures falling within the range varying betweenabout 925 F. and about in the following table: 6 gaseous phase, attemperatures falling within the Example No 1 2 8 4 5 6 .ParamnlcHydrocarbon Reactan Propane Propane lsobutane Isobutane N-butaneN-haptanc. Moi Ratio: Ammonia to Par aifinlc Hydrocarbon Reacton 2:1..2:1.. 2:1" M 2:1- 2.7:1. Temperature, F 985 1050 981) 1025 950 920.

Contact Time, is. 0.1-. 0.7.- 0.1 0.7- 0.1 0.9.

Producto l. Aoetonltrile i. Acetonltrile l. Aoetonitrilc l. Acetonitrilol. Acetonltrlle LAoetonitrile encompasses carbon Beactant 2.8. 8.9. 2 46.2.. 4.4.... 0.5.

. 2. Propionitrile 2. Propiohitrlle 2. Propionitrilc 2. Butyronitrilo2.- Propionitrilc Yield per-pass trace 1.4-... r m traea.... 1.4.

3. Proplonitrile 8. rile Dc.. trace 3.0.

It will be apparent that the present invention range varying betweenabout 925 IF. and about provides an eflicient, inexpensive and safeproc- 1075 F., in the presence of a molybdenum oxide ass for obtainingnltriles. Our process is of consupported on a. catalyst support.siderable value in making available relatively in- 6. A process for theproduction of nitriles havezpensive nitriles which are useful, forexample, ing at least two carbon atoms per molceule,'whichasintermediates in organic synthesis. comprises contacting propane withammonia, in

This applicant is a continuation-in-part of cogaseous phase, attemperatures tailing within pending application, Serial Number 539,032,filed the range varying between about 925 F. and June 6, 1944, nowabandoned. about 1075 F., in the presence of molybdenum Although thepresent invention has been detrioxide supported on alumina. scribed 'inconjunction with preferred embodi- 7. A process for the production ofnitriles havments, it is to be understood that modifications ing atleast two carbon atoms per molecule, which and variations may beresorted to without departcomprises contacting a butane with ammonia, ining from the spirit and scope of the invention, as gaseous phase, attemperatures falling within the those skilled in the art will readilyunderstand. range varying between about 925 F. and about Such variationsand modifications are considered 6% 1075 R, in the presence of acatalyst comprising to be within the purview and scope of the apamolybdenum oxide. pended claims. 8. A process for the production ofnitriles hav- We claim: ing at least two. carbon atoms per molecule,which A Pr for the Production of mmles comprises contacting a butanewith ammonia, in ing at least two carbon atoms per molecule, which Mgaseous phase, at temperatures falling within the comprises contacting aDaramnic hydrocarbon range varying between about 925 F. and about continin at least two and p o abo t ten car- 1075- F., in the presence of amolybdenum oxide bon atoms per molecule, with ammonia, in gassupportedon a catalyst support. eous phase, at temperatures falling within the 9,A rocess forthe production of nitriles havran V y between about F. andabout ing at least two carbon atoms per molecule, which 1075 F in the Prn of a atalyst comprising comprises contacting a butane with ammonia, ina molybdenum oxide. gaseous phase, at temperatures falling within the 2.A process for the production of nitriles havrange varying bet n ab t 925F, and about me at least two carbo ato s pe molecule. which 1075 F., inthe presence of molybdenum trloxide comprises contacting a parafilnichydrocarbon supported on alumina containing at least and to about ten10. A process for the production of nltriles havbon atoms per moleculewith ammonia" in ing-at least two carbon atoms per molecule, which wasphase at temperatures mixing within the comprises contacting a heptanewith ammonia, in rang? varying between about 925 and about gaseousphase, at temperatures falling within the 1075 F., in the presence of amolybdenum oxide ran ge varying between about 925 F. and about supportedonacatalyst support. F 1 m f t l t m 3. A process for the production ofnitriles havn 9 presence 0 ca ys comp ing at least two carbon atoms permolecule, which mflybdenum oxidecomprises contacting a parammchydrocarbon 11. A process for the production of nitriles havcontainingat'least two and up to about ten cari s at least two carbon atoms p m ll which bon atoms per molecule, with ammonia, in gascomprises contactingtan wit ammonia. in I eous phase, at temperatures falling within thegaseous phase, at temperatures falling within the range varying betweenabout 925 F. and about range varying between about 925 F. and about 1075F., in the presence of molybdenum trioxide 1075 F., in the presence of amolybdenum oxide supported on alumina. supported on acataiyst support.

12. A process for the production of nitriles having at least two carbonatoms per molecule, which comprises contacting a heptane with ammonia,in gaseous phase, at temperatures falling within the range varyingbetween about 925 1". and about WW 1"., In the presence of molybdenumtrloxide UNITED STATES PATENTS Name Date Jaeger Aug. 1, 1933 Forney Oct.19, 1943 Teter Aug. 7, 1945 Teter Aug. 7, 1945 Teter Aug. 7, 1945 TeterAug. 7, 1945 Apgar et a1 Aug. 7, 1945

